Effect of nitrogen on the high coercivity and microstructures of Co-Ni alloy films

Abstract

Co‐30 at. % Ni alloy films containing N up to 18 at. % were deposited to thicknesses of 100 and 400 nm by rf sputtering in the atmosphere of Ar‐N₂ mixture and they were annealed. Most of N included diffused out from the film surface after annealing. The concentration of N, (C_nf) before annealing, however, has a significant effect on the coercive force, Hc, and the formation of the microstructures such as hollow channels and c axis preferred orientation parallel to the film plane in the annealed films. The preferred orientation factor, R, has a minimum, and Hc has a maximum in a film with C_nf of 13–15 at. %. There is a linear relation between Hc and R; Hc=Hc₀(1−R/R₀). The values of Hc₀ tend to decrease with the film thickness, and they slightly depend on the microstructures, such as the hollow channels and grain boundaries.